| dc.description.abstract | In this dissertation, we investigate the Schottky performance of the material of InAlGaP in contact with the Schottky Ti/Pt/Au metals. We use different chemical solutions to treat the InAlGaP surface to improve the Schottky diode performance. We also employ wide bandgap In0.5(Al0.66Ga0.34)0.5P (referred to as InAlGaP, hereafter), lattice-matched to GaAs, for the capping layers and buffer layer in the GaAs MSM-PDs, to improve the performance of the MSM-PDs. We also use the photoelectrochemical oxidation method to directly grow the oxide film of GaAs and InAlGaP between the interdigital electrodes of MSM-PDs for a passivation layer. This reduces surface defects and improves the performance of the passivated MSM-PDs.
First, we compare the characteristics of Au/Pt/Ti/InAlGaP/GaAs Schottky diodes with different chemical solutions treated the InAlGaP surface. The chemical solution treatements include buffered oxide etchant (BOE), diluted HCl and diluted NH4OH. Among the various surface treatments mentioned, the best Schottky performances are achieved after using NH4OH+10H2O for 30sec to treat the InAlGaP surface. The ideality factor and the Schottky barrier height are 1.10 and 1.08eV, respectively, and the highest breakdown voltage is –58V. We also investigate the characteristics of Au/Pt/Ti/InAlGaP/GaAs Schottky diodes treated with NH4OH+10H2O for various times (10sec, 30sec, 60sec and 90sec). The results of TEM (transmission electron microscopy) and AFM (atomic force microscopy) measurement are also used to analyze the degradation mechanisms of Schottky diodes treated with diluted NH4OH for various times. The best Schottky performances are achieved using NH4OH+10H2O for 30sec to treat the InAlGaP surface.
We employ the wide bandgap InAlGaP material for the capping and buffer layers in GaAs MSM-PD structure, to effectively reduce the dark current and avoid the low-frequency internal gain. The dark current of the InAlGaP/GaAs MSM-PDs is 70pA at –10V. In this study, we also investigate the possibility of evaluating the main Schottky contact parameters directlyfrom the InAlGaP/GaAs MSM-PD structure. The MSM-PDs are illuminated by different optical powers (semiconductor laser, wavelength of 841nm); the measured photoresponsivity is 0.28A/W. The spectral photoreponsivity is determined with a monochromator and a Xe lamp source.
Finally, to improve the stability of MSM-PDs, we use a photoelectrochemical oxidation method to directly grow the oxide film of GaAs and InAlGaP between the interdigital electrodes of MSM-PDs. This acts as a passivation layer to reduce surface defects. From the experimental results, we see that the process of oxide passivated can reduce the dark current and increase the breakdown voltage of MSM-PDs. | en_US |